Currently, as a technology which enables with ease a high speed, miniaturization, and an increase in the size of copying machines and laser beam printers (hereinafter, “LBP”), an electrophotographic photoreceptor belt wherein the electrophotographic photoreceptor is formed in the shape of a belt has been developed.
The electrophotographic photoreceptor belt has an advantage that a metal drum having a large diameter as conventional photoreceptors is not required and a wider photoreceptor can be developed in the same volume. Therefore, it is suitable for downsizing of an equipment and high-speed printing of a large-sized print such as a poster.
The mainstream of an electrophotographic photoreceptor belt is that wherein a charge generating layer and a charge transport layer are formed on a conductive support belt substrate such as a film of stainless steel or an aluminum metallized polyethylene terephthalate. Among them, photoreceptor belts wherein polycarbonate is used for a charge transport layer are known. Among them, electrophotographic photoreceptor belts which are intended to prevent cracks and improve wear resistance after long-time repetitive use are known (see Patent Document 1, Patent Document 2 and Patent Document 3).
Currently, the demand of copying machines and LBPs overseas has been increased, and these machines are occasionally exposed to an unexpected use environment depending on the circumstances in each country. Especially, in the tropics, they are constantly exposed to an environment under high temperature and high humidity and are susceptible to a history where temperature and humidity are largely varied depending on on-off of an air conditioner in the room. In this case, the electrophotographic photoreceptor belt mounted in a copying machine or LBP tends to generate stress due to difference of linear expansion coefficient of the metal film side which does not cause hygroscopic expansion and the resin film part which readily cause hygroscopically expansion.
Therefore, occasionally, cracks or image failures generate on the surface of the belt in a shorter cycle than the expected number of service times, and thus improvement is required.
Meanwhile, for the purpose of preventing the curl of an electrophotographic photoreceptor belt, use of a belt-rear-side reinforcing film is known. While the rear side reinforcing film is effective for preventing the curl, it occasionally is insufficient in wear resistance of the reinforcing film or is insufficient in crack resistance of the electrophotographic photoreceptor belt exposed to an environment under high temperature and humidity, and thus improvement is required (see Patent Document 4).    Patent Document 1: Jpn. Pat. Laid-Open Publication No. H8-152723    Patent Document 2: Jpn. Pat. Laid-Open Publication No. H10-111579    Patent Document 3: Jpn. Pat. Laid-Open Publication No. 2000-10315    Patent Document 4: Jpn. Pat. Laid-Open Publication No. H10-213917